Large quantities of hydrazines are used as fuels. The toxicity and possible carcinogenicity of the vapours require air monitoring for personnel safety.
Known hydrazine sensors are generally complex. For example, FR-A-2331791 discloses a gas detector apparently capable of detecting low levels of (dimethyl)hydrazine in air, comprising a combination of an ionisable detector and a gas scrubber.
U.S. Pat. No. 3549329 discloses a sensor for reducing vapours, including hydrazine and unsymmetrical dimethylhydrazine, comprising a noble metal thin film partially covered by a thin layer of a reducible metal salt; the salt lowers the electrical resistance of the film when exposed to the reducing vapour.
Polypyrrole-coated chemiresistors, sensitive to ammonia, are known.
Miasik et al, Conducting Polymers, Alcacer (ed.), D.Reidel Publishing Company (1987) 189-197, disclose forming thin polypyrrole films by electropolymerisation from aqueous solutions of the monomer and LiBF.sub.4. The film was sensitive to 0.1% ammonia in air, and also sensitive to other gases.
Ojio et al, Polymer Journal 18(1) (1986) 95-98, disclose transparent, conducting polypyrrole-polyvinyl alcohol composite films formed by exposing PVA films containing ferric chloride to pyrrole vapour. The properties of the polypyrrole film are apparently similar to those of polypyrrole prepared by electrochemical polymerisation.
Armes et al, J. Chem. Soc., Chem. Commun. (1987) 288-290, disclose the preparation of conducting polypyrrole particles by dispersion polymerisation in aqueous medium, using ferric chloride as the initiator. A concentrated system was used, and stirring was maintained for at least 16 hours.